1. Technical Field
This invention relates to tire depth determining systems and, more particularly, to a vehicle tire tread depth determining system for warning a driver of low tread depth on a vehicle tire.
2. Prior Art
Pneumatic vehicle tires essentially consist of a tire carcass, which consists of plies of rubberized fabric, and tread rubber, which surrounds the exterior surface of the carcass. In belted tires, additional layers of fiber glass, steel, or aramid are placed between the plies and the tread rubber. During manufacture, the tire is vulcanized to gain its final shape and strength characteristics. Besides equalizing the stresses within the tire body, the vulcanization changes the rubber compound into a tough, highly elastic material and bonds the parts of the tire into one integral unit.
During the vulcanization process, the tread rubber is molded to form the tire treads which provide frictional engagement between the tire and the road surface. The treads also protect the tire carcass from foreign obstacles on the road surface which could damage the carcass. Since the effectiveness of the tire tread as a cushioning and protective sheath is dependent upon the amount of tread rubber covering the carcass, this effectiveness is decreased as the treads are reduced by wear. If the tire is not routinely inspected, the tread may be worn down to a level where driving becomes dangerous.
One prior art example shows a tire with a layer of a colored material embedded in the tread rubber to visually indicate the degree of tread wear. The tire includes positioning plies having colored fibers at different tread depths to visually indicate when the tread has been worn to the point at which the tread should be recapped or the tire replaced. A second prior art example shows a tire having a sub-surface tread portion of a color contrasting to the outer portion of the tread to indicate when the tread is worn. Another prior art example shows a tire with a colored indicating means embedded within the tread portion of a tire. In this case, the indicating means is preferably made from rubber, metal, or plastic.
Problems have arisen in connection with the above-described colored tread wear indicators in that the coloring in the indicators degrades under the high temperature of vulcanization. Moreover, in instances when the colored material is formed from plastic, the colored material may not sufficiently adhere to the tread rubber. Consequently, after the tire cools following vulcanization, air pockets may remain between the plastic tread wear indicators and the tread rubber, thereby reducing the integrity of the tire.
Accordingly, a need remains for a vehicle tire tread depth determining system in order to overcome the above-noted shortcomings. The present invention satisfies such a need by providing a system that is convenient and easy to use, is lightweight yet durable in design, and provides an easy and effective means of notifying a driver that a tire is excessively worn and should be replaced. Such a system is advantageously enclosed in a sturdy casing that is effectively embedded in the tire tread. When exposed to the ground surface, the system conveniently shows a yellow strip on the worn tire, effectively indicating that a new tire is needed. The system includes an effective visual alert system conveniently mounted on the dashboard of the vehicle, thus advantageously providing a lighted indicator of tire tread status that is visible while driving the car. The significantly and effectively decreases the risk of injuries or fatalities that result from motorists driving on worn or bald tires, thus advantageously helping to keep roadways safe while driving.